1. Field of the Invention
The disclosure relates to a three-dimensional integrated circuit (3-D IC), and more particularly, to a 3-D IC and a method capable of repairing a memory chip after the chip is stacked with a controller chip.
2. Description of Related Art
A 3-D IC stacks and connects chips vertically by using the through-silicon via (TSV) technology. A TSV is an electrical conductor which passes completely through the silicon substrate of a chip. By introducing the vertical interconnect, a system design allows accessing the front side of the chip from the backside or vice versa. The length of the TSV is about equal to the thickness of the chip, and is usually shorter than 100 μm. Hence, a long wire between two components on a system on chip (SoC) may be eliminated by placing the two components on two separate chips and routing their connection through the TSV, so the propagation delay can be reduced significantly. In addition, the density of the TSVs may be higher than 100/mm2, and therefore, the TSVs may provide a high bandwidth in the 3-D IC.
At present, a spare memory (having multiple spare memory cells that are added into a memory array typically in a form of redundant row or redundant column) is usually built in a memory chip, so as to replace a damaged memory cell if there exists one.
However, even a well tested and repaired memory chip may be damaged again during the process of TSV forming, wafer thinning, and chip stacking of the 3-D IC. At this time, the spare memory may not be used up, but the chip stacking should be announced as a failure, because it is impossible to record any newly added failure address after chip stacking. Using a conventional method of programming by laser excision, for example, the front side of a chip after stacking may be covered by an upper- or lower-layer chip, and unable to have a fuse be blown. Obviously, as it fails to repair the memory chip by replacing the damaged memory cell with a spare after chip stacking, the enhancement of manufacturing yield of the 3-D IC becomes one of the major tasks at present.